Conventional circuit arrangements for starting a gas discharge lamp which, in order to provide an AC supply voltage, is assigned a supply circuit, which has at least one inductor connected in series with the gas discharge lamp, are designed as heterodyne starting circuits. Such a starting circuit is disclosed for example in the German published patent application DE 19531622. It comprises a pulse transformer whose secondary side can be connected to the lamp for transmitting a starting pulse and whose primary side is connected to a starting triggering circuit for triggering a starting pulse. The starting triggering circuit includes an input energy source and a first switch means that is controlled by an electronic control device.
The timing of the starting process, particularly the generation of the starting pulses, is coupled to the phase position of the AC supply voltage to make sure that the starting pulses are generated at times at which the lamp can start and burn due to the instantaneous supply voltage. Moreover, conventional starting circuit arrangements provide that after the production of first starting pulses additional starting pulses are produced in a fashion adjusted to the AC supply voltage or that also other processes are initiated which assist the starting process.
In this respect, conventional starting circuit arrangements require the scanning of the instantaneous phase position of the AC supply voltage during or shortly after starting so that the starting process can be adjusted to it as described.
To this end, conventional starting circuit arrangements normally comprise at least three inputs which are directly connected to the phase of the AC supply voltage, to the output of the inductor respectively to the neutral conductor of the mains. The above-described applies to the connection to conventional single-phase mains. If the lamp and thus the starting circuit arrangement are operated on multi-phase mains, the first input terminal of the conventional starting circuit arrangement is connected to the L1 terminal of the mains, the second input terminal of the starting circuit arrangement is connected to the output of the inductor, and the third input terminal of the starting circuit arrangement is connected to the L2 terminal of the mains. Accordingly, in both cases the phase of the supply voltage can be scanned, thus providing for a starting control whose timing is adapted to the mains voltage.
FIG. 4a shows such a conventional starting circuit arrangement for starting a discharge lamp including three inputs B, L, N. The main voltage UN is applied to the input terminals L, N, and the lamp inductor 110 is connected in series with the input terminal B. The L input of the conventional starting device 100 on the one side serves to supplying the internal control circuit and on the other side to scanning the mains voltage so that the starting process can be synchronized with the mains voltage. On the output side, the starting device 100 includes two terminals to which the discharge lamp 3, e.g. a high-pressure gas discharge lamp, is connected.
Especially in applications in which the respective lamps are arranged remotely from the inductor of the supply circuit, this arrangement including a conventional starting circuit has disadvantages.
The complexity of the wiring at the use of such a conventional starting device is illustrated in FIG. 4b using floodlights as an example. The lamp inductor 110 is usually arranged in a distribution cabinet 105 which is usually placed with a distance to the light pole 120 and in which the lamp supply circuit is connected to the mains voltage. The distance between the distribution cabinet and the starting circuit may easily be more than 100 m. The pole carries a lamp array 130, and the associated starting device is arranged in direct neighborhood of the lamps. As it becomes apparent from the described illustration, the line 140 between the distribution cabinet and the lamp 130 must have a three-pole design, since the conventional starting device includes an inductor terminal as well as the input terminals L, N for the mains voltage UN.
The fact that conventional starting circuit arrangements usually have three input terminals means that the wiring is very complex.